Re: [dpdk-dev] [PATCH] test/test: improve dequeue logic for crypto operation

["De Lara Guarch, Pablo" <pablo.de.lara.guarch@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Akhil Goyal
> Sent: Thursday, April 20, 2017 11:48 AM
> To: De Lara Guarch, Pablo; dev@dpdk.org
> Cc: Doherty, Declan; hemant.agrawal@nxp.com
> Subject: Re: [dpdk-dev] [PATCH] test/test: improve dequeue logic for crypto
> operation
> 
> Hi Pablo,
> 
> On 4/4/2017 8:41 PM, De Lara Guarch, Pablo wrote:
> > Hi Akhil,
> >
> >> -----Original Message-----
> >> From: akhil.goyal@nxp.com [mailto:akhil.goyal@nxp.com]
> >> Sent: Monday, April 03, 2017 11:53 AM
> >> To: dev@dpdk.org
> >> Cc: Doherty, Declan; De Lara Guarch, Pablo; Akhil Goyal
> >> Subject: [PATCH] test/test: improve dequeue logic for crypto operation
> >>
> >> From: Akhil Goyal <akhil.goyal@nxp.com>
> >>
> >> While enqueue/dequeue operations in test_perf_aes_sha,
> >> the underlying implementation may not be able to dequeue
> >> the same number of buffers as enqueued. So, it may be
> >> necessary to perform more dequeue operations if the gap
> >> is more than pparams->burst_size * NUM_MBUF_SETS.
> >>
> >> Other algos may also need to update the logic if required.
> >>
> >
> > In which way this patch improves the dequeue logic?
> > Is it improving the performance somehow? From what I see, it is unlikely
> that you are going to
> > experience the problem, as the internal ring is PERF_NUM_OPS_INFLIGHT,
> which is 128,
> > higher than pparams->burst_size * NUM_MBUF_SETS, which is 256.
> > And even if you do meet that problem, then you would be reusing mbufs,
> > but that is OK as we are not verifying the output.
> >
> >
> > Thanks,
> > Pablo
> >
> Sorry for the late response. Somehow the reply went to junk in my mail
> client and it got missed.
> 
> The problem would arise if the underlying implementation cannot dequeue
> the same number of ops as were enqueued in a single dequeue command.
> 
> Here we have a synchronous calls to enqueue and dequeue in the same
> thread, so it may happen that for every enqueue of 32 ops, there are
> lesser number of dequeue ops (say 16). There is no thread to dequeue the
> left over 16 ops. So the difference would increase slowly and gradually
> and the application will run out of buffers.
> So we need a mechanism to drain the left over dequeue ops.

Hi Akhil,

I understand, I guess that this won't happen on a software device, but might happen on hardware.
As said, I think it is OK to reuse an mbuf by two different crypto operations, because we don't check the output.

Anyway, it might be safer to proceed your way. Two things about it, though:
1 - This should be extended to the other tests (such as test_perf_openssl) for consistency.
2 - Since we have the test-crypto-perf app now, which cover all these tests, I was thinking of removing test_cryptodev_perf.c,
to avoid duplications. Any concerns on this?

Thanks,
Pablo

> 
> Regards,
> Akhil
> 
>